Whether the embryo breathes in the womb.

Further one inquires whether the embryo breathes in the womb.

1. And it seems it does. A proper operation arises at the same time as the power to which it belongs. But respiration is the operation of the lungs and heart, since it is bestowed upon an animal to temper the heart's heat. Therefore, since the heart and the lungs appear in the embryo, then respiration will be present in the embryo.

2. In addition, the heart's heat is assisted in two ways: through nutriment and through respiration. Since, then, it is nourished in the womb, it will, by the same argument, breathe in the womb.

To the contrary. Respiration occurs through the nose and the mouth. But these parts are not open on the fetus in the womb. Therefore, it does not breathe.

One must reply to this that the embryo does not breathe in the womb, since respiration is the drawing-in of air; but this cannot happen in the womb. Nor does it need this drawing action, since in the womb the embryo abounds with a great deal of moisture and can adequately temper the heat of the heart, and this is why it does not have to be tempered from another source. But when the fetus is outside the uterus, its moisture does not cease to be diminished, nor do its exterior parts cease to be dried out by contact with the outside.[1] Therefore, at that time the heart's heat begins to burn, and this is why it then needs respiration.

1. On to the arguments. To the first, one must reply that respiration is not the heart's proper operation, since many animals that have a heart do not breathe, but the heart's motion, or pulse, is more appropriate to the heart, and thus pulse can exist in the embryo by means of the natural spirits that are generated in the arteries and perpetuated by being continuously received by the womb.

2. To the second argument one must reply that the reasons for the embryo's nutriment and for its respiration in the womb are not the same, because, while the fetus is in the womb, the nutriment there suffices for two. With this a solution is apparent for this argument.

Whether sleep occurs in the embryo.

Whether waking precedes sleep.

Further one inquires whether sleep occurs in the embryo in the womb.

1. It seems not. For sleep is a hindrance to the external senses. But in the womb the embryo does not operate with external senses. Therefore, properly speaking, it neither dreams nor wakes nor sleeps.

2. In addition, "the embryo lives a life like a plant in the womb." But a plant neither sleeps nor wakes. Therefore, etc.

The Philosopher says the opposite.

Further one inquires whether waking precedes sleep, or contrariwise.

3. And it seems that waking precedes sleep. Because the first act precedes the second and a path precedes an end. But waking is to sleep just as a first act is to a second, and just as a path is to an end, since it is related to sleep just as motion is to rest. Therefore, waking precedes sleep.

4. In addition, the deprivation of some characteristic is a privation. Therefore, since sleep is a kind of privation, it necessarily presupposes a wakefulness held earlier.

5. To the contrary. What crosses from one extreme to the other approaches the midpoint before it reaches the extreme. But sleep is just like the midpoint between living and non-living. Therefore, crossing from non-living to living, one must first pass through sleep just as through a midpoint.

To the first question one must reply that "sleep is a hindrance to the first sensitivity [primum sensitivum]," according to the Philosopher in On Sleep and Waking. But the first sensitivity exists in the embryo, which is apparent because, if it is pricked or approached by something harmful, it moves. Therefore, this sensitivity can labor in response to excessive [stimulus]. This [stimulus], however, brings on tiredness born of labor. Tiredness in an animal's sensitive parts induces sleep, and this is why sleep occurs in the embryo in the womb.[2]

1. On to the arguments. To the first, one must reply that act is of two types, first and second, and the second is also of two types, namely, internal and external. In the embryo there is the first act of sensation, and there is a second act there also with respect to the internal but not to the external. Because although a person's eyes close voluntarily, he nevertheless is not always sleeping when his eyes are closed, and, likewise, if he actively sees nothing at all at night, he nevertheless is not always sleeping. Rather, he can be asleep at one time and awake at another. And thus the embryo exists in the womb just as the eye exists in darkness or when veiled by the eyelids. Therefore, the fact that it does not operate with respect to what is external is owing to a defect of its eyes.

2. To the second argument one must reply that the embryo lives the life of a plant before it lives the life of an animal, and it is said to live the life of a plant because it does not employ its sensitive power with respect to what is external, just as a plant does not. This is why, etc.

To the other question one must reply that sleep is properly caused by the rising of the vapors to the brain, since some vapors clog and block the spirits' pathways to the individual senses. Therefore, one can say that sleep precedes waking in the embryo, because the senses of the embryo are blocked and hindered for a long time by the multitude of fumes. And this is why sleep precedes waking.

Or one can say to the contrary that waking precedes sleep, because an act is of two types, namely, first and second, and a proper waking state corresponds to each, and sleep corresponds to each waking state as its state of rest. Therefore, if a uniform comparison is made, a waking state precedes its own proper sleep state. Now it is clear that as soon as the fetus is born it screams and cries, which are acts of a waking state. And it is the same if one were to compare the waking state of a first act to its sleep state.

3, 4. With this a solution is apparent to the first arguments.

5. To [this] argument one must reply to the contrary that, although it might attain sleep before it lives perfectly or completely, nevertheless it does not attain sleep before it attains the waking state, because the large size of its head and the multitude of vapors confer sleep upon it, and these exist in children after their first birthday. And this is why, when children are in their first stage of growth, they sleep a great deal, but when they attain an older age, they sleep less because the vapors are consumed.

Or one can say in another way that sleep is not the midpoint between living and non-living, since these are contradictories. But one who is dreaming or sleeping cannot be said to be nonliving, nor can he be said to be living in terms of a second act. And because it is not a true midpoint, it is not necessary that he attain sleep first.[3] This is just as matter can be said to be the middle between being and non-being, and it is nevertheless not necessary for something crossing from non-being to being to pass through matter first. And this is why, etc. Through this a solution to this one is apparent.

  • [1] "By contact with the outside": per continens. Continens has been used in this work to indicate anything which surrounds and contains something else, e.g., an eggshell. It may therefore indicate the external environment here.
  • [2] The Latin of this portion is exceptionally vague.
  • [3] I.e., he does not have to pass through sleep before he can become awake.
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